local notification is not displayed - ios

Question

I'm working on a Xamarion iOS app. I want to display a local notification when an event occurs in my app, Like Outlook does when an email is received.
I'm using the following code, after having received the right to send notification from the user, of course:
var content = new UNMutableNotificationContent();
if (!string.IsNullOrWhiteSpace(value: mySoundFile))
{
content.Sound = UNNotificationSound.GetCriticalSound(mySoundFile);
}
if (!string.IsNullOrEmpty(myChannelDescription))
{
content.ThreadIdentifier = myChannelDescription;
}
content.Title = "MyTitle";
content.Body = "MyText";
var trigger = UNTimeIntervalNotificationTrigger.CreateTrigger(0.1, false);
var request = UNNotificationRequest.FromIdentifier(notification.Id.ToString(), content, trigger);
var center = UNUserNotificationCenter.Current;
center.AddNotificationRequest(request, null);
But the notification is not displayed.
Any help appreciated.

Answer 1

The reason for not displaying the notification could be several things. Try the following solutions:
Make sure that the application has the required rights to send notifications and that the user has enabled them.
Check if the sound file is valid and located in the application package. It may also be necessary to add it to the Info.plist file.
Check if the thread identifier is valid and not repeatable.
Check if the trigger time is valid. Setting 0.1 seconds is very short and may not be enough to display the notification.
If the above solutions do not work, it is worth using debugging tools to more closely examine why the notification is not displayed.

Answer 2

On iOS, you must request permission to use notifications before attempting to schedule them. Just like this, you can try to check if the following code is added to your project:
UNUserNotificationCenter.Current.RequestAuthorization(UNAuthorizationOptions.Alert, (approved, err) =>
{
...
});
You can change your AddNotificationRequest as follows to see if there is an error in the notification：
center.AddNotificationRequest(request, (err) =>
{
if (err != null)
{
throw new Exception($"Failed to schedule notification: {err}");
}
});
For more details, you can refer to the following documents to check some permission issues:
Enhanced User Notifications in Xamarin.iOS | Microsoft
Asking permission to use notifications | Apple Developer
UpDate: If your app is in the foreground. You could try implementing the delegate userNotificationCenter(_:willPresent:withCompletionHandler:) which will be called when a notification arrives while the app is in the foreground. Refer to the following code:
UNUserNotificationCenter.Current.Delegate = new TestDelegate();
public class TestDelegate: UNUserNotificationCenterDelegate
{
public override void WillPresentNotification(UNUserNotificationCenter center, UNNotification notification, Action<UNNotificationPresentationOptions> completionHandler)
{
completionHandler(UNNotificationPresentationOptions.Alert);
}
}